A direct-methanol fuel cell has a cell structure provided with an anode which comprises a current collector and a catalytic layer formed on this current collector and into which an aqueous methanol (CH3OH) solution is introduced as a fuel, a cathode which comprises a current collector and a catalytic layer formed on this current collector and into which an oxidizer is introduced and a proton conductive membrane interposed between these anode and cathode in such a manner that it is in contact with each of these catalytic layers. Each catalytic layer is formed of a mixture of a catalyst and Nafion™ (manufactured by DuPont), which is a perfluoroalkylsulfonic acid polymer. The Nafion™ in each catalytic layer is superior in chemical stability and also serves to support the catalyst. Incidentally, Nafion™ is also used as the structural resin of the proton conductive membrane which is an electrolyte membrane.
In a fuel cell having such a cell structure, when ethanol (C2H5OH) as a pollutant in an atmospheric is introduced together with air as an oxidizer into the cathode, it contaminates the catalyst in the catalytic layer of the cathode to degrade catalytic activity. The ethanol diffuses from sources such as alcoholic drinks and cosmetics to an atmospheric.